The invention relates to a method for mounting a fiber composite component in the force flow of a clamping connection.
When fiber composite components are secured by clamping, the problem arises that, as a result of the settlement behavior of the fiber composite, the pretensioning force of the clamping connection decreases over time.
The term “settlement” describes the yielding of the material under the pretensioning force which is introduced therein when tightening a clamping connection. This effect may, for example, be brought about in plastics materials by the creeping of the plastics material under loading.
In order to reduce the loss of pretensioning force, for example, when screwing the fiber composites, metal bushes are introduced therein. Doing so is, however, complex and expensive.
An object of the invention is to provide a method by which the assembly of fiber composites in clamping connections is possible in a simpler manner.
To this end, in a method for mounting a component of a fiber composite in the force flow of a clamping connection, the following steps are provided:
(ii) heating the fiber composite, at least in an assembly region; and
(ii) locally compressing the heated fiber composite in the assembly region so that the fiber composite settles to a predetermined degree; and
(iii) clamping the component of the fiber composite in the assembly region.
As a result of the local compression of the heated fiber composite, there is produced in the assembly region an accelerated settlement operation, in which the thickness of the component is advantageously substantially already reduced to the extent which corresponds to the natural settlement operation without previous compression and heating. Since over time a smaller additional settlement of the material is carried out, the pretensioning force of the clamping connection is substantially maintained since the component gives way only to a small extent under the pretensioning force of the clamping connection. With this method, it is possible to allow a clamping force to act directly on the composite fiber component without the pretensioning force of the clamping connection significantly decreasing over time.
Preferably, the steps of heating and compressing are carried out prior to the step of installing in a clamping connection and separately therefrom, for example, in a device which is provided separately for this purpose.
In order to carry out the compression, the component is clamped, for example, between a die with a pressing face which corresponds to the assembly region and a retention member counter-face, wherein the pressing force which is required for the local settlement of the fiber composite is applied between the die and retention member counter-face.
In order to bring about the local action of temperature on the assembly region, for example, the die and/or the retention member counter-face can be heated.
The temperature of the die and/or the retention member counter-face during the compression may, for example, be from 80° C. to 250° C., in particular approximately 100° C. In this instance, the component of fiber composite is heated during the compression or prior to the compression preferably to from 80° C. to 250° C., in particular to approximately 100° C.
It is also possible to heat the component itself directly. This may be carried out, for example, in an external oven prior to the compression. If the fiber composite is electrically conductive, for instance, when carbon fibers are used, the component may also be heated to the desired temperature by means of a direct or induced current flow. Optionally, the heating may remain locally limited to the assembly region.
It has been found that compression with a surface pressure of from 20 to 140 MPa provides good results.
The duration of the compression may, for example, be from 1 to 5 minutes, in particular approximately 3 minutes.
In another variant, the fiber composite of the component is already mounted in the actual clamping connection prior to the local compression and this is used for the local compression, wherein the fiber composite of the component is heated at least in the assembly region. The heating may take place in this case as described above by means of heating in an external oven prior to the assembly and/or by means of the supply of heat during the compression, for example, by way of a current flow through the assembly region or another suitable type of local heating. The pressing force required for the accelerated settlement process during compression is in this instance applied by the clamping connection. After the assembly region has completed the compression operation and the component has cooled again, the clamping connection is finally tightened in order to definitively mount the component.
In the fiber composite component, at least one opening for a securing device may be introduced in the assembly region, for example, so that screw connections through the component are also possible.
It is possible to use as fiber composites in particular fiber-reinforced plastics materials, preferably those with a polymer matrix material. It is possible to use as reinforcement fibers, for example, carbon fibers, glass fibers, aramide fibers and/or basalt fibers, but also natural fibers such as, for example, hemp fibers. When continuous filaments are used, these can be embedded in the matrix as an interlaid scrim, braid and/or woven textile.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.